Management treats its junior staff as disposable. They actually have a brilliant, money-saving strategy, which works for them.
It's very hard to get a junior level position outside the internship program, which is a cutthroat program in which only the best are offered a job, if one is even available (don't believe them if they promise one is, many people have been fooled into staying for six months as cheap labor and kicked to the curb).
When people are finally hired, they are thrilled to be an official member of the Edelman family, so they are convinced that they love their job, despite the abuse of their time and lack of compensation. The starting salaries after the internship are low, and people get small increases (~2-3% on average, 5% if you're lucky) annually, which compounds to a still small salary. Still, the internship burns into the culture that you are lucky to be there, so you stay, though switching companies would get you a vastly greater salary and a superior work/life balance.
You won't be paid a livable wage. Even if you did have money to spare, you wouldn't have time to spend it on hobbies because you won't consistently leave the office at a reasonable hour. You're expected to be on call at all times (I personally was tracked down at 4 am and nonstop weekends for a three-month period), and was negatively reviewed for not signing up for additional weekend coverage immediately following that quarter. It's common for employees to stay until 8 or 9 pm, or later. Edelman promotes the "work hard, play hard" mentality, which is just another way of saying you work late and maybe crack open a beer with your colleagues at 9 pm when there is still work to be done. Suffice it to say that the people on the 24/7 cycle are junior staff.
The people who, bolstered by blatant favoritism, don't burn out, eventually rise through the ranks, but most stagnate at middle management until they are pushed out.